The abstract of an article in a recent edition of Science Magazine says:
“Most prior studies have found that substituting biofuels for gasoline will reduce greenhouse gases because biofuels sequester carbon through the growth of the feedstock. These analyses have failed to count the carbon emissions that occur as farmers worldwide respond to higher prices and convert forest and grassland to new cropland to replace the grain (or cropland) diverted to biofuels. Using a worldwide agricultural model to estimate emissions from land use change, we found that corn-based ethanol, instead of producing a 20% savings, nearly doubles greenhouse emissions over 30 years and increases greenhouse gases for 167 years. Biofuels from switchgrass, if grown on U.S. corn lands, increase emissions by 50%. This result raises concerns about large biofuel mandates and highlights the value of using waste products.”
Europeans trying to comply with Kyoto mandates have proposed stipulating that biofuels used to meet their alternative fuel mandates cannot come from land that was previously rain forest. However, the study points out that such restrictions are window dressing. Food, like energy, is fungible. If European biofuels come only from existing agricultural land, the food crops formerly grown there will be grown somewhere else; good chance that somewhere else will be newly cleared.
A New York Times article by Elizabeth Rosenthal about the studies published in Science gives this example:
“…Previously, Midwestern farmers had alternated corn with soy in their fields, one year to the next. Now many grow only corn, meaning that soy has to be grown elsewhere.
“Increasingly, that elsewhere, Dr. Fargione said, is Brazil, on land that was previously forest or savanna. ‘Brazilian farmers are planting more of the world’s soybeans — and they’re deforesting the Amazon to do it,’ he said.”
The studies do point out that biofuels made from agricultural waste (technologies for which are being worked on but have not yet been made remotely economical) and that biofuels from sugar – as made in Brazil and, inexplicably to me, not made in any quantity in Hawaii – would and do have a positive carbon impact.
Defenders of the subsidized biofuels industry are quick to point out that biofuels do help energy independence. On a global basis, use of farmland to “grow energy” diversifies energy sources – a good thing – and increases income to farmers in poor as well as wealthy areas – another good thing. On the other hand, diversion of cropland raises food prices.
The world economy isn’t as complex as the environment but it may be as chaotic and hard to model. Food prices and the amount of land under cultivation would both be going up now even without corn-based ethanol production because the huge number of people escaping poverty in India and China are using some of their new income to eat more and better – as well as to buy motorcycles and cars.
In the long term it seems foolish to use plants to convert sunlight to energy for fuel when solar collectors – after a huge capital outlay and with big infrastructure changes – yields one hundred times more energy per acre than growing corn. Moreover, some of the best places for solar generated electricity are not cropland because they are arid.
But now it seems that corny ethanol may not be a good short term solution either. Suppose, for example, we burn more coal even before we have a way to sequester or divert the atmospheric carbon dioxide produced. Even giving full credit to the most alarming predictions of carbon-based global warming, this may be environmentally more friendly than clearing a rain forest. You can stop burning the coal if you can’t sequester the CO2 or whenever replacement energy comes online; you can’t replant the rain forest. Hmm…
Some will argue reasonably that discrediting ethanol as a panacea is one more reason why conservation (aka less driving in smaller cars) is the only solution to the twin problems of energy independence and global warming. Trouble with that thinking is that the aforementioned newly unpoor aren’t going to forgo the pleasures of personal transportation which we have long enjoyed. We need more energy sources.
The math behind my claim that solar produces 100 times the yield of corn in net energy per acre at 1800 times the capital cost is here.